Trunnion tilt corrector



Jan. 12, 1960 -w. H. NEWELL ETAL 2,920,817

TRUNNION TILT. coRREcToR Filed July 27, 195s 4 sheets-sheet 1 n Imventors M//M/A/v H. Nin/fu LAWRENCE S. BIOWNl L/00 (Ittorneg Jan. 12, 1960 w, H, NEWELL ETAL 2,920,817

TRUNNION TILT CORRECTOR Filed July 27, 1953 4 Sheets-Sheet 2 l nnentors H//u//w A( /VfWf/ LAWRENCE S. BROWN Jan. 12, 1960 w. H. NEWELL Erm. 2,920,817

TRUNNION TILT CORRECTOR 4 Sheets-Sheet 3 Filed July 27, 1953 v Snventors l/I/MUA/v A. A/fwfLL LAWRENCE S WOW/V Jan. 12, 1960 w. H. NEWELL ET Ax. '2,920,817

TRUNNION TILT coRREoToa 4 Sheets-Sheet 4 Filed July 27, 1953 2,920,817 TRUNNIoN TILT coRREc'roR William H. Newell, Mount Vernon, and Lawrence S.

Brown, Massapequa, N.Y., assignors to Sperry Rand Corporation, a corporation of Delaware Application July 27, 1953, Serial No. 370,256

Z Claims. (Cl. 23S-61.5)

corrected to determine certain tire control quantities.

The so-called computer in a tire control system provides a continuous solution for the train and elevation of a particular target and must operate relative to the horizontal plane. However, the line of sight (involveither optical or radar tracking) is determined by the director of the fire control system, relative to the deck plane. The conversion of director information to define the line of sight relative to the horizontal plane is accomplished by the deck tilt corrector. It is necessary for accurate firing, to convert the line of bore (gun axis) coordinates in the horizontal plane as determined by the computer back into coordinates relative to the deck plane, by means of a trunnion tilt corrector.

The mechanization of trunnion tilt correctional equations which are not true solution equations introduces errors affecting adversely the accuracy of determination of trunnion tilt correction quantities.

One object of the present invention is to provide a new and improved method and instrument, by which the necessary values of trunnion tilt correction, are accurately and continuously computed, thus eliminating the eiiect of angular movement of the de'ck and causing thereby the system to operate accurately as if said system were supported upon a stable platform.

As a feature of the present invention, there are derived true solution formulas for certain trunnion tilt correctional angles interms of available quantities. From the main computing section of the re control system, there is available (l) the elevation angle betweenthe line of f gun bore and its projection on the horizontal plane and (2) the horizontal sight projections of the line of bore and the line of sight and from the stableelement on the ship, there is available (3) the level angle between vthehoizo'ntal and deck planes measured in the vertical plane through the line of sight and (4) the cross-level angle between the vertical plane through the line of sight and a plane perpendicular to the deck plane through the projection of the line of sight on the deck plane. From these four available quantities, true solutionfrr'nulas are "deivd in accordance with the present invention for,(l) the deck sight deflection angle between the vertical planeV through the line of sight and the plane perpendicular to the deck plane through the line of bore, as measuredA in the deck plane and (2) the elevation correction angle deiined by where E'g is the angle between the line of bore and its projection on the deck plane, Eg Vis th'e elevtionnigl available as indicated above and L is the level angle available Vas indicated above.

l(bhPh) Train Parallax Correction for "2,926,817, Patented Jan. l2, 1960 The trefsolution formulas are mechanizedwith the four available quantities described above as inputs, to give continuous solutions for the deck sight deflection angle and the elevation correction angle defined above. Each of the formulasl is solved continuously for a corresponding trunnion tilt correction by a servo or null seeking system, which so drives the trunnion tilt correction line, that a balance is obtained between the quantities on opposite sides of the equality sign of the formula.

Various other objects, features and advantages of .the present invention are apparent from the following particular' descriptionl and from an inspection of the accompanying drawings, in which y Fig'. 1 is a simplified block diagram showing the function relationship betweendiierent components of a suitable gun iire control system, into which the trunnion tilt corrector of the present invention may be incorporated; Fig. 2 is a simplified block diagram showing a gun order device or network which forms part of the lire control system of Fig. 1 and which includes the trunnion tilt corrector of the present invention;

Fig. 3 is a spherical diagram of the trunnion tilt problem solved in accordance with the present invention; and

Fig. 4 is a simplified block diagram of the trunnion tilt corrector embodying the present invention.

A tabulation ofk symbols and terms used in the derivation of formulas herein, in the drawings and in the description is submitted herein:

(Bg) Gun Train Order Angle-the ordered angle between the vertical plane through the. ships centerline and the vertical plane through the gun bore axis, measured in the deck plane clockwise from the bow.

(B"r) Director Train Angle-the angle between the vertical plane through the ships centerline and the vertical plane through the line' of sight, measured in the deck plane-clockwise from the bow.

gun directors horizontal base. t

(bh'.P`v) Elevation Parallax Correction for gun direcf tors horizontal base. Y A

(Dd) Deck Sight Deflection Angle-The angle between the vertical plane through the line of sight and the plane perpendicular ,to the deck plane through the line of bore of the gun (gun axis), as measured in the deck plane.

(Dh) Horizontal Sight Deflection Angle-the angle between the vertical plane through the line of sight and the vertical plane through the line of bore, measured in the horizontal plane, clockwise from the vertical plane through the line of sight.

(Eg) Vertical Gun Elevation yAngle--the angle between Vthe ,liner of bore 'and its projection on the' horizontal plane. u p (Eg) Gun Elevation Order Angle-the ordered angle -between tlieline of bore and its projection on the deck plano. ,1...

(l.) Level `Angle-the angle between the deck plane and the horizontal plane measured in the vertical plane through the line of sight, this angle being positive when the portion of the deck towards the target yis down.

(Vz) Correction Angle to Gun Elevationcompensating for trunnion tilt and deiined by V'zrA-E'g- (Eg-l-L).

(Zd) Cross-Level 'Anglethe angle between the vertical plane through therline of sight andthe planeperpendi'cularto the deck plane through the intersection of the deck plane and the vertical plane through the line of sight.

A suitable tire control system capable of solving gun re control problems both anti-aircraft and surface is illustrated in simplitied form in Fig. l. This tire control system may comprise a computer assembly 10, a gun director 11, and a stable element 12. The computer assem bly 10 includes a prediction network for determining horizontal sight deflection Dh and ver/ticall gun elevation Eg, a parallax correction network for determining 4train parallax correction (bh.Ph) and'elevation parallax correction (bh,Pv), and a gun order device or 'network shown in simplified form in Fig. 2. This gun order de- 14, which is the subject ofthe present invention and which operates in conjunction with a number of adding components or diierentials 16, 17, 18 and'19 to make up the gun orders from (1) the Dh and Eg outputs from the prediction network, (2) the (bh.Ph) and (bh.Pv) outputs from theparallax correction network, V(3) the L and the Br output from the gun director 11V (Fig. 1). vThe trunnion tilt corrector 14 in this gun order network has The gun elevation order Eg and gun train order B'gr are computed by the gun order device or network of Fig. 2 according to the following equations:v

Gun elevation order `Eg is sent to the gun mounts while gun train order Bgris sent to the gun mounts and the parallax correction network.

In accordance with the present invention, true solutions for the trunnion tilt problems vare'employed, thereby eliminating errors, such as those which would be inherent, if empirical solutions were employed. As a result of the procedure of lthe present invention, true solution formulas are obtained for trunnion tilt corrections Dd (deck deection) and Vz (elevation correction) in terms of the available quantities Eg (elevation order), Dh (defle'ction order), L (level) and Zd (cross-level). These formulas are solved for trunnion tilt corrections Eg and Vz by servo or null seeking systems which so position the Dd and Vz lines, that a balance is obtained between the quantities represented by the `right and left hand Yterms ofreach equation. f The trunnion tilt correction problems are indicated in the spherical diagram shown in Fig. 3. These problems are solved in accordance with true solutions, using as inputs the vertical gun elevationfEg and the horizontal fsight deflection Dh obtained from the prediction network f of the computer 10 (Fig. l) and the level L and crosslevel Zd obtained from the stable element 12 (Fig. 1).

Dd solution From the spherical trigonometry of Fig. 3, the following relationship can be ascertained inputs Dh, Eg, L and Zd and outputs (L+Vz) and Dd. v

vice or network may comprise a trunnion tilt corrector Zd outputs from the stable element 12 (Fig. 1), and (4) v 10) tan Dd=tan P cos Zd see (U-i-L) tan D d By constructing great circle arc C in Fig. 3:

Substituting 14 in 1l:

substituting s iu 7 "cos wwwmw .fj

sin T cos Zd Y Cos Dd sin Zd (9) sin Dd=sin (M-i-U-l-L) sinT v sin Dd t sin (M+1U+L) Substituting-8 and 9 in 6 y sin Dd=cos Dd tan P cos Zd cos (U-i-L) +eos 'Dd v sin T tan Dd= cos (U+L) s cos Zd tan P A oosU'cos L-sin U sin L MM :M y l-tan U tan L cos C=cos Picos U cos C=cos Eg cos Dh (12) cosP cos U=cos Eg cos Dh In trianglecomprised by P and the zenith sin P=sin (90-Eg) sin Dh=cos Eg sin Dh Substituting 15 in 1 0 and expanding tan (U-i-L) lcos Zd tan Dh sec Lei-sin Zd tan U-l-sin Zd tan 1-tan U'tan L cos Zd tan Dd seo L sin Zd tan U-l-sin Zd tan L Deiining Vz as follows:

vSubstituting 26 and 27 in 25 6 GOS (Vel-Dh) sin N=Sn Zd* Substituting 29 in 28 thev spherical triangle comprised by (90*'Eg) (29) (9o-U), and P;

.f g- U P..' 90-E` i cos( )ccs COS( g) sin zd sin Dh Y L h l (17) sin U-'l-sS-E-'lg 5 (30) tan i cos D tan L cos N From 12 (31) cos N=cos L cos Zd (is) cos MMM Substituting 31 in so COS P (32) tan L1=tan L cos Dh-tan Zd sin Dh sec L Substituting 23, 24 and 32 in 22 1 sin g=sin Eg cos L cos Zd-l-cos Eg cos L cos Zd tan L cos Dh-cos Eg cos L 'I l cos Zd tan Zd sin Dh secL From 17 and 18 sin tari Eg (19) tan U=cos Eg cos Dh-cos Dh Substituting 19 in 16 cos Zvd tan Dh sec L-i-sin Zd tan Eglisi'n Zd tan L Y Y Y cosDh r. Y tan Dd l-mn Eg tan L Vcos Dh cos Eg cos Dh-sin Eg S L sin Dd cos Zd sin Dh cos Eg-l-sin Zd sin Eg cos L-l-sin Zd vsin L cos Eg cos Dh cos Ddcos Eg cos Dh cos L-sin Eg sin L (20)v sin Ddicos Eg cos Dh cos L-sin Eg sin L] (33) sin Eg=sin Eg cos L cos *Zdi-cos' Eg'sin L cos Zd cos Dh-cos Eg sin Zd sin Dh i =cos Dd (cos Zd sin Dh cos Eg-l-sin Zd sin v y Eg cos L-l-sin Zd sin L cos Eg cos Dh) From `the spherical diagram of Fig. 3, the following Equation 20 constitutes the solution equation for vthe 35 rlatlonshlp can be ascertamed: Dd servo inthe mechanization of the equation. Voltages (34) cos E'g cos Dd=cos P cos (U-l-L)=='cos P y in accordance with the left hand side are applied in oppocos U cos L-cos P sin U sin `L site sign to those of the iight hand side to the servo error detector. The servo then positions itself such, that the Substituting 12 and 17 m 34 v equation is balanced and its dial reads the computed (35) COS Eg cos Dd=cos Eg cos Dh value of Dd for the particular values of the input quanticos L-sin Eg sin L ties at the moment- Rearranging Equation 33 VZ solution (36) sin Eg cos L cos Zd-l-cos Eg sin L cos Zd cos Dh-cos Eg sin Zd f sin Dh=sin E'g Multiplying corresponding sides of 35 and 36 (37) Q cos Eg cos Dd= (cos Eg cos Dh cos L-sin Eg sin L) sin E'Ag From the spherical trigonometry of Fig. 3, ythe follow- Sing relationships vcari be ascertained:

(Eg-l-L) sin EgL-sin (Eg-l-L) cos Zd Q=(S1n Eg cos L cos Zd-l-cos Eg sin L cos Zdd i h (22) sin g=s'in Eg cos L1 cos Zl-l-cos Eg ccs Dh-cos Eg sm Z M D sin L1 cos Z1 cos N=cos L1 cos Z1 55 This Equation 37Vconstitutes the solution equation for cos N=cos L cos Zd the VZ SGIVO- Although Vz does not appear explicitly in the equation, its solution is effected by includingit Where (23) cos L1 C95 Z1=COS L cos Zd through a differential resolver in the quantity (24) sin L1 cos Z1=cos L co's Zd tan L1 E E L (25) tan L1=sin V tan N tan L=sin (V-l-Dh) tan T 60 g: g+ +Vz 26 t N tan L1 The solution Equation 20 for obtaining the quantity an sin (V-l-Dh) Dd (deck sight deflection), must be rearranged and equated to zero, to determine the polarity of each of the two main computation channels for mechanization.

0=cos Dd (cos Zd sin Dh cos Eg-l-sin Zd sin Eg cos L-l-sin Zd sin L cos Eg cos Dh)sin Dd (cos Eg cos Dh cos L-sin Eg sin L) Expressing V as (V-leDh) -Dh (27) sin V=sin (V-l-Dh) cos Dh-cos (V-l-Dh) sin Dh .tan L Sil (V-l-Dh) COS Dh tim L Therefore, the Equation 20 to be mechanized for the 1 Sin (V-l-Dh) quantity Dd involves the following two main channels:

-cos (V+ Dh) sin Dh tan N g (2S) (1) cos Dd (cos Zd sin Dh cos Eg-l-sin Zd sin v tan L1=s Dh tan Lcos (V+ Dh) sin Dh sin N cos L-l-sm Zd sin L cos Eg cos Dh) S N 'i5 V(2) @-sinDd (cos Eg cos Dh Acos L-sin Eg sin L) In a smilarmannen'the solution Equation 37 for obtaining the quantity Vz (elevation correction) must be rearranged and equated to zero, to determine the polarity of each of the -twomain computation channels for mechanization:V

=Q cos E'g cos ,Dd-. (cos Eg cos Dh cos L-sin Eg sin L) sin Eg Where I. K i Q=(sin Eg cos L cos Zd-F-cos Egsin L cos Zdcos Dh-cos Eg `sin Zd sin Dh) Therefore, the Equation 37 to be mechanized` for the quantity Yz involves lthe following two main channels y I(3) YQ cos Eg cos Dd (4) -(cos Eg cos Dh cos L-sin Eg sin L) sin Eg The computer for solving the Equation 20 is essentially one in which quantities in the form of the proper functions of input and output quantities are added, subtracted and multiplied in each of the channels of computation 1 and 2. From Equation 20, it is seen that the summation of these two channels 1 and 2 should be zero. Consequently, the output of a two input differential or adding device, is used as a servo` input to drive a line in accordance with the quantity Dd. When the servo nulls the output of this adding device, the equation of this solution has been satisfied.

Similarly, the two channels of Computation 3 and 4 are fed as inputs into an adding device to obtain an output which is used as a servo input and which when nulled, satisfies theEquation 37, thereby producing a line drive .according to the quantity Vz.`

N Ihe trunnion tilt corrector employed for the mechanization of Equations 2O and 37 is made up of a series of components, which may be of any suitable design, and which per se, form no part of the present invention. Fig. f4 therefore, shows this trunnion `tilt corrector diagrammatically in block form. The specific corrector .shown as an example, is essentially an electrical one, the solid lines indicating electrical connections and the dotted lines 4indicating rmechanical lines or movements arising, for

example, from shaft rotations.

The specific trunnion tilt corrector shownin Fig. 4 utilizes 400 cycle per sec. A.C. as a computing reference, with an input level of 12 volts,-the representation of ldata `by the 40G-cycle voltage being such, that the root mean square value of each voltage is proportional to the quantity represented. For the purpose of discussion, this reference voltage is regarded as (+1). The different "com'putedquantities are indicated in Fig. 4 without parametric coeflicients. These coeflicients are a function of the reference voltage (12 volts) and the characteristics of the constituent elements of the networks or loops involved'and are constant for any one mechanism.

Channel 1 cos Eg-i-sin Zd sin Eg cos L Y +sin Zd sin L cos Eg cos Dh) The main components employed in the mechanization of Equations 20 and 37 aside from the servo mechanlsms 4,cos (cos Zd sin Dh Y,are angle function computers or resolvers. These relsolvers may be of any suitable type, as for example, of

lthe magnetic type disclosed in application Serial No.

"of windings andy comprises essentially of a stator having two separate distributed windings arranged in space quadrature and constituting primary windings and a rotor hav- .fing twoseparate distributed windings in space quadrature constituting secondary windings.

f'. In' operation, the specificmagnetic yresolver described .1.

lISIS :acts asa single-'phase transformer with- Aa variable coupling between primary and secondary. As thev rotor turns, the voltage across'each secondary winding changes. Construction ofthe resolver is such that the secondary voltages vary as the sine or cosine of the angle through which the rotor turns. In some resolvers, both rotor and stator can turn.

In operation, the angle as a mechanical quantity turns the rotor. A voltage energizes-the stator. Assuming the stator to be fixed, voltages corresponding to the product of the stator energizing voltage and sine and cosinelof the angle are computed at the rotor windings. If instead of being fixed, the stator is turned through an angle in the opposite direction to the rotor, the outputs are proportional to the sine and cosine of theV sum of the `stator and rotor angles. If the stator is turned through an angle in the same direction as the rotor, the outputs are proport ional to the sine and cosinerof the differencebetween the two angles.

Where two voltagesv are' imposed upon the resolver in conjunction with the mechanical input whose trigonometric function is tobe computed, these two voltages are algebraically added in the resolver in any suitable manner before being impressed upon the stator. Y

In some cases, the resolver may include a differential to add quantities for resolution into the 'trigonometric functions.

, Since it is impracticable to design a computing resolver that has no outputvoltage wave-shape distortion and,

therefore no appreciable error, the basic resolver circuit described gives onlyapproximate results. Reduction ofv the error to a negligible amount israccomplishcd by an error compensating loop described in the aforesaid application'Serial No. 157,892, now Patent No. 2,646,218. This error compensating loop attenuates the distortion by introducing a high gainl amplifier ahead of the computing resolver'and connecting an error compensating resolver in parallel with the computing resolver and to the output of the amplifier. identical electrically andmagnetically with the computing .resolver andthe two resolvers may have a common primary (stator). The output of error compensating re.- solver is fed back as a negative feed-back to the input of the amplifier. The rotorof this error compensating resolver is set by adjustment and clamped to obtain correct output voltages from the computing resolver.

In the following description of the trunnion tilt corrector, it is assumed that the resolvers mentioned are of the magnetic type described, although they may be of any suitable type.

In the mechanization of computation channel 1, a reference voltage (12 volts) and the mechanical elevation quantity (Eg) as computed'in the main computing section of the fire control system, are fed as inputs into a resolver 21. The sin Eg voltage output of this resolver v21 and the mechanical level quantity (L) obtained from thevstable element of the ship are fed as inputs into a resolver 22, and the cos Eg voltage output of the resolver 21 and the mechanical horizontal sight deflection quantity Dh, as computed in the computer 10 (Fig. 1), of the re control system, are fed as inputs into a resolver 23. The cos Eg cos Dh voltage output of the resolver 23 and the mechanical level quantity (L) are brought into a resolver 24. The cos Eg cos Dh sin L voltage output of this resolver 24 and the sin Eg cos L voltage output of this resolver 22,-totally (sin Eg cos L-l-cos Eg cos Dh sin L) volts, are fed into a resolver 25 in conjunction with the mechanical cross-level quantity '(Zd) obtained from the stable element of the ship. The voltage output cos Eg sin Dh from the resolver 23 is delivered to a resolver 26 in conjunction with the mechanical cross-level quantity (Zd), and the voltage output cos Eg sin Dh cos Zd from this resolver 26 and the voltage output (sin Eg cos L-i-cos Eg cos Dh sin L) sin Zd from the resolver 25, totally (sin Eg cos L' 'sin Zd-i-cos Eg cos Dh sin L sin Zdicoa This error compensating resolver is.

Eg sin Dh cos Zd) volts, are fed into a resolver 27 into which is also delivered the mechanical deck sight deflection quantity Dd obtained from the output of the trunnion tilt corrector in the manner to be described. The voltage output of this resolver 27 is cos Dd (sin Eg cos L sin Zd-l-cos Eg cos Dh sin L sin Zd-i-cos Eg sin Dh cos Zd) which is the desired quantity of channel 1.

Channel 2 -sin Dd (cos g cos Dh cos L-sin Eg sin L) In the mechanization for computation channel 2, the voltage output sin Eg sin L from the resolver 22 and the voltage output cos Eg cos Dh cos L from the resolver 24, totally (cos Eg cos Dh cos L-sin Eg sin L) volts, are fed as inputs into a resolver 28, having as a mechanical input the deck sight deection quantity (Dd) obtained from the output of the trunnion tilt corrector to produce a sin Dd) operator in the resolver 28. The vo-ltage output of this resolver 28 is (cos Eg cos Dh cos L-sin Eg sin L) sin Dd which is the desired quantity of channel 2.

Produclon o'f (Dd) fom channels 1 and 2 The two voltage outputs of computation channels 1 and 2 are conducted to a suitable summing device 32, which may be an adding network, comprising two input resistors in parallel, a computing amplifier at the common connection of these resistors having a very large gain, so as to draw no significant current from this point and to maintain this connection at a zero potential, a feedback resistor and a load resistor. The different resistance ratios are selected to convert the two input voltages to a common scale, i.e., to the same value per volt.

Theoretically, according to Equation 20, the summation of the computation channels l and 2 should be zero. If the conditions of the Equation 20 are not satisiied, an error is produced at the output of the summing device 32, which in the case of an electrical system such as that of Fig. 4, is a voltage having the proper polarity to drive the servo motor of a servo mechanism 33 of the wellknown type, to produce a null in the error voltage. When this null is achieved, the value of (Dd) converted into a mechanical quantity (shaft rotation) becomes one of the trunnion tilt correction quantities.

A servo mechanism, such as the servo mechanism 33, is an automatic drive which positions a mechanical load in accurate correspondence with an input, without placing an appreciable load upon this input. The input can be either mechanical or electrical (in Fig. 4, the input is electrical) but the output is always mechanical.

The basic components of the specic servo mechanism shown in Fig. 4 comprises a servo control 34, a servo amplier 35, a servo motor 36, and an induction generator 37, connected in a double loop circuit with a control network which in the present case is the summing loop 32. Essentially, the control network 32 computes a voltage proportional to the error between a function of the input and a function of the output. This error voltage is converted to a frequency of 60 cycles by the servo control 34, amplified by the servo amplifier 35 and finally supplied to the servo motor 36 for its control. The servo motor 36 furnishes the mechanical output and drives the induction generator 37. From this generator 37, a voltage proportional to the output velocity is supplied to the servo control 34. After being modied by computing elements in the servo control 34, the modified voltage is combined with the error voltage to improve the operation of the servo mechanism.

The output mechanical quantity (Dd) from the servo mechanism 33, which is the quantity sought is fed back as a mechanical input into the resolvers 27 and 28, for the purpose already indicated.

Channel 3 Q cos Eg cos Dd where Q= (sin Eg cos L cos Zd-I-co's Eg sin L v cos Zd cos Dh-cos Eg sin Zd sin Dh) In the mechanization of computation vchannel 3, the voltage output (sin Eg cos L-i-cos Eg cos Dh sin L) cos Zd from the resolver 25 and the voltage output cos Eg sin Dh sin Zd from the resolver 26 are fed into a resolver 29, and the sum of these voltage outputs is multiplied by the operator cos Dd in the resolver 29 to produce the voltage output Q cos Dd. This latter output from the resolver 29 is fed into a resolver 30, into which is also fed -as inputs the mechanical elevation quantity Eg, as computed in the computer 10 (Fig. 2) of the fire control system, and the mechanical summation quantity (L-l-Vz) obtained by adding mechanically in any suitable manner, the level (L) derived from the stable element and the elevation correction quantity Vz derived as on'e of the outputs of the trunnion tilt corrector, in a manner to be described. The operating factor cos (Eg-i-L-l- Vz) or cos Eg computed in the resolver 30 from these mechanical input quantities are multiplied therein by the inputvoltage Q cos Dd to obtain a voltage output from said resolver 30 corresponding to the quantity Q cos Dd cos E which in turn corresponds to the desired channel 3.

Channel 4 (cos Eg cos Dh cos L-sin Eg sin L) sin Eg In the mechanization of computation channel 4, the voltage output cos Eg cos Dh cos L from the resolver 24 and the voltage output sin Eg sin L) from the resolver 22 are fed as inputs for addition into a resolver 31, into which is also fed as inputs the mechanical quantity Eg and the mechanical summation quantity (L-l-Vz), as in the case of the resolver 30. The operating factor sin (Eg-|-L+ Vz) or sin Eg computed in the resolver 31 from these mechanical input quantites is multiplied therein by the sum of the voltage inputs into said resolver to produce the voltage output cos Eg cos Dh cos L-sin Eg sin L) sin Eg corresponding to the desired channel 4.

Production of (Vz) from channels 3 and 4 The two voltage outputs of computation channels 3 and 4 are conducted to a suitable summing device 40, which may be an adding network similar to the adding network 32.

Theoretically, according to Equation 37, the summation of the computations 3 and 4 should be zero. If the conditions of the Equation 37 are not satislied, an error is produced at the output of the summing device 40, which in the case of an electrical system such as that of Fig. 4, is a voltage having the proper polarity to drive the servo motor of a servo mechanism 41, similar to the servo mechanism 33, to produce a null in the error voltage. When this null is achieved, the value of (Vz) converted into a'mechanical quantity (shaft rotation) becomes one of the trunnion tilt quantities required.

Equations 20 and 37 mechanized by the trunnion tilt corrector 14 of the present invention can be expressed in different forms, as for example, by the substitution of trigonometric equivalents, without altering the basic substance of the equations. It should be understood therefore, that the references to the specific equations in the following claims cover such equivalent substitutions.

In the following claims, by mechanical operation, mechanizing, and kindred terms it is intended to cover not only the use of strictly mechanical expedients but also electrical devices as well.

While the invention has been described with particular reference to a specific embodiment, it is to be understood that it is not to be limited thereto, but is to be construed broadly and restricted solely by the scope of the appended claims as interpreted in-accordance with the above explanation.

What is claimed is:

1. A d-evice'- for Icontinuously computing the deck sigh deection angle (Dd) for trunnion tilt correction in a gun re control system, comprising means for continurously mechanizing for the quantity (Dd), the equation containing the two main group terms as follows:

0="cos Dd (cos Zd sin Dh cos Eg-l-sin Zd sin Eg cos L+ sin Zd sin L cos Eg cos Dh)-sin Dd (cos Eg cos Dh cos L-sin Eg sin L),

wherein (Eg) represents the vertical gun elevation angle, (Dh) the horizontal sight deflection angle, (L) the level angle and (Zd) the cross-level angle, said mechanizing lmeans including two computation channels with outputs corresponding to said 'main group terms respectively,

means for adding said-channel outputs, and a' servofmechanism for driving a (Dd) line having as input the output of said adding means. v

' '92. A device for continuously computing the correction angle to gun elevationV (Vz) for trunnion tilt correction in a gun tire control system, comprising means for continuously mechanizing for the quantity (Vz), the

`equation containing the two main group terms as follows: 0='Q,cos- Eg cos Dd'r(cos Eg cos DhV Acos L-sin Eg 4sin L) sin Eg,

l'wherein Q=(sin Eg cos L cos Zd-l-cos Eg sin L cos Zd cos Dhcos Eg sin Zd sin Dh),

References Cited in the file of this patent v UNITED STATES PATENTS 2,463,687

Gittens Mar. 8, 1949 2,486,781 Gittens Nov. 1, 1949 2,658,674 Darlington Nov. 10, 1954 2,824,693 James Feb. 25, 1958 

